1. Field of the Invention
This invention relates to pipe joints with premium threads and more particularly to joints used downhole in a producing well. The invention may be used with drill pipe, tubing or casing, all of which are referred to herein as "pipe".
2. Description of the Prior Art
For many years couplings with threads formed on their inside diameter have been used to attach two relatively long sections of pipe to each other. Examples of such couplings are shown in U.S. Pat. No. 2,980,451 to W. B. Taylor et al; U.S. Pat. No. 4,004,832 to Eugene B. Connelly; and U.S. Pat. No. 3,497,246 to P. D. Weiner. U.S. Pat. No. 2,980,451 also discloses the use of elastomeric or polymeric seal rings to form a fluid barrier between the inside diameter of the coupling and the outside diameter of the portion of pipe disposed therein. U.S. Pat. No. 2,980,451 is incorporated by reference for all purposes herein.
An alternative to the use of couplings has been to upset (enlarge the wall thickness by mechanical means) the end portions of sections of pipe. Appropriate male and female threads are machined on the upset ends to provide a pin means and box means respectively for joining sections of pipe with each other. Examples of such pipe joints and associated premium threads are shown in U.S. Pat. Nos. 3,489,437 to J. L. A. Duret and 3,100,656 to M. D. MacArthur. The premium thread and sealing system of the present invention can be satisfactorily used with either couplings or upset type pipe joints.